The invention relates to a circuit configuration for the controlled filling and refilling of containers with liquids by means of an input flow control unit that is responsive to electrical means implementing an intermittant supply of the liquid, and more particularly for beverage mixers having a water processing container, to which the water to be processed can be fed by means of a feed pump in accordance with one of two water-level values measured by a water-level sensor system.
It is common practice, for example, to produce blended beverages immediately before they are consumed by using a mixture consisting of carbonated water and beverage concentrates. To prepare this carbonated water, a storage tank, preferably cooled, is employed in a manner well known to those skilled in the art. Quantities of carbonated water are fed, as required, from this storage tank. Accordingly, the ingredients, i.e., CO.sub.2 gas and fresh water, must be supplied to the tank. To supply CO.sub.2 gas to the storage tank, the latter is connected to a CO.sub.2 supply cylinder via a pressure-reducing valve assembly. To fill and refill the storage tank with fresh water, the latter is connected to a water supply line. A flow input control unit controls the input feed in accordance with the water level in the storage tank. This water level is measured by sensors which, in the interest of a simple design and simple signal processing, are preferably constructed by means of a series-connected sensor circuit. If an adequate water pressure is present in the supply line, the flow input control unit can merely be realized by means of a valve assembly that can be triggered by electrical means. However, if one cannot assume with certainty that sufficient water pressure will continuously be available in the supply line, it is necessary to provide a pump unit as a flow input control unit in conjunction with an appropriate valve assembly. The water supply pressure must be sufficiently high, because the water--at least as the storage tank is being filled--must be supplied against the pressure of the CO.sub.2 gas.
It is worth considering for what mode of operation the supply flow control unit, be it the electrically triggerable valve assembly or the pumping installation, is utilized since the operating mode has a bearing on the manufacturing costs, on the functioning, and on the size of the control unit. During normal operation, for example in beverage dispensers, the supply flow control units merely operate in intervals and, on an average, the idle intervals last longer than the working intervals. However, malfunctions can occur, which prolong the working intervals by different amounts, so that the input flow control units are triggered for indefinitely long periods. Therefore, as a safeguard against such occurrences, the input flow control unit is made to be of the continuous-duty type. Also, for the majority of liquid-pumping installations, a so-called "dry run" is particularly dangerous because the result is that neither the bearing points will be lubricated, nor will the pump unit be cooled, and this leads to overheating and damage to the bearings in the pump unit. Such a dry run of the pump unit is to be feared if a water-requirement level is signaled from the storage tank while, due to a variety of reasons, and no water is available.
Therefore, the object of the invention is to provide a circuit configuration that makes it possible to design an input supply control unit for a conventional beverage dispenser, and providing essentially trouble-free, operation, but wherein this unit, in the event of a malfunction, is protected against undue overloads, increased wear and destruction. For a storage tank in a beverage dispenser having a water capacity of approximately 2 liters, normal operating conditions prevail if the empty storage tank can be filled within approximately 90 to 150 seconds and can be refilled within 30 to 45 seconds when portions of carbonated water are withdrawn for the preparation of beverages.